For those wondering, just search for skimlinks and MNHQ. Here’s one explanation from Justine back in 2012
“JustineMumsnet
Yes these links are meant and it is a revenue thing. We've had skimlinks on the site for a bit in the form of an auto affiliate thing when people type in links. We make a decent amount of revenue from it - not loads but enough to pay for one of our servers and it seems reasonably unobtrusive. They've recently suggested we try linking to shop mentions too. I'm not quite sure how they choose them - think it's just who they have in their client list.
We hope it's not too intrusive - and that it might actually be mildly useful. We would certainly never do those pop up auto message links attached to keywords that you see on some sites and have turned those down a few times.
In any case do not be alarmed, your device hasn't gone doolally. And it won't be skimlinks making the site run slow - more likely server capacity. Will try to get to the bottom of it tomorrow.”
And more recently
www.mumsnet.com/Talk/site_stuff/2845367-Skimlinks-on-Talk
AmyGMumsnet
“Hi folks,
Some of you might have spotted a few more links in discussions across the site - this is because we're testing out a programme called Skimlinks, which auto-converts some of your brand mentions into links.
This makes it easier for you to have a look at products that other MNers happen to mention on the boards, and, if you decide to make a purchase from one of these links, Mumsnet benefits from a small commission.
Thanks all - let us know if you experience any issues that you think might be related.”